From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id A4F293858291 for ; Thu, 27 Oct 2022 10:09:30 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A4F293858291 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666865370; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=kB6UTlFdNfqvMqiCugVAMmROlxbdGMNc9iCsVdBFyec=; b=PEwPuqqLaCEULRprD7Xhl60yXkcTAjsOHOXS6qkNR7lTs4FjpPJORofec5CkZWjFBmVE6t mcQX7AHYQOSG5jV2D+YGn+7sMGTwCWPqq6+8Id9eLn4XBBOIveQQwpsYTwm6s7vZENNGKP VSvBFS+1HeIENg6bDgRueBkPu2JRwUo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-132-Fz4-0I4SNWmTf1-mv7qxrw-1; Thu, 27 Oct 2022 06:09:27 -0400 X-MC-Unique: Fz4-0I4SNWmTf1-mv7qxrw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CAD38101A54E; Thu, 27 Oct 2022 10:09:26 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.74]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2676B200C0DA; Thu, 27 Oct 2022 10:09:26 +0000 (UTC) From: Florian Weimer To: Paul Eggert Cc: libc-alpha@sourceware.org Subject: Re: [PATCH] manual: Add more documentation for the tm_isdst member of struct tm References: <87zgdl4c75.fsf@oldenburg.str.redhat.com> <806730c1-81d4-6601-8ecf-d1b8b322c324@cs.ucla.edu> <87r0yx0vtc.fsf@oldenburg.str.redhat.com> <68a8ff7f-75af-7e58-5f6e-0357eb76fc6a@cs.ucla.edu> <87h6zrwzdg.fsf@oldenburg.str.redhat.com> <874jvqvnih.fsf@oldenburg.str.redhat.com> <6b01632f-047c-c18f-5616-4037bfe706fa@cs.ucla.edu> Date: Thu, 27 Oct 2022 12:09:24 +0200 In-Reply-To: <6b01632f-047c-c18f-5616-4037bfe706fa@cs.ucla.edu> (Paul Eggert's message of "Wed, 26 Oct 2022 12:05:07 -0700") Message-ID: <87ilk5r31n.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-4.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: * Paul Eggert: >> Maybe we should just document that applications should set this field to >> -1 when constructing struct tm data? > > Yes, if you're deriving struct tm data from the outside world and you > have no idea what tm_isdst etc. should be, your apps should set > tm_isdst to -1. However, if the outside world tells you tm_gmtoff > (which is pretty common these days, e.g., see the "Date:" line in this > email), then your apps should also set tm_gmtoff to what the outside > world tells you, before you call mktime. Okay, that would indeed be helpful advice. I'll see if I can come up with a new patch. >> In case of Ireland it seems an artificial complication, though. The >> perception seems to be that IST is summer time, not standard time > > My impression is different, in that people in Ireland typically say > "summer time" or "winter time". They typically do not say "standard > time" or "daylight saving time". And as it happens, summer time = > standard time in Ireland. I think RTE is not exactly fringe media in Ireland, and they recently wrote (largely copying from last year I admittedly): | When do the clocks change in Ireland in 2022? | | Daylight saving time in Ireland began (went forward an hour) at 01:00 | on Sunday, 27 March 2022 and will end (go back an hour) at 02:00 on | Sunday, 30 October 2022. This is not just one journalist making an error. I think the cultural convention *is* different. Thanks, Florian